Thousands of schoolchildren in the UK are being recruited for the world's largest study on the impact mobile phones have on things like memory and attention span.

The Study of Cognition, Adolescents and Mobile Phones, or SCAMP, will assess 2500 11 and 12-year-olds over three years.

It will examine whether mobiles and other wireless devices affect children's cognitive functions, such as their ability to make decisions and process information.

The project is being funded by the Department of Health, partly using money from the mobile phone industry, and is being led by researchers from Imperial College London.

More than 160 secondary schools in the outer London area will today receive invitations to take part.

The principal investigator for the study, Dr Mireille Toledano, told Sky News: "These cognitive functions are continuing to develop (in these schoolchildren) which are so essential to our everyday life - to their ability to read, their basic skills in maths, intelligence and educational achievement.

"It is absolutely essential - and the most responsible thing for us to do when mobile phone usage is so widespread in our children (is) to be able to provide evidence to reassure the public, hopefully, that there are no adverse effects."

Image Caption:Seventy percent of 11 and 12-year-olds in the UK have a mobile phone

Parents and pupils who agree to take part in the study will answer questionnaires about the children's use of mobile devices and wireless technologies.

Pupils will do computerised tests to measure their brain function and some will also wear monitors to assess their exposure to radio waves.

Some 70% of 11 and 12-year-olds in the UK now own a mobile phone and by 14 that goes up to 90%.

Most research so far on mobile phones has focused on adults and the risk of brain cancers.

While there is no convincing evidence that radio wave exposures from mobile phones affect health, scientists remain uncertain as to whether children's developing brains are more vulnerable than adult brains.

The World Health Organisation (WHO) has already said that research into the impact on adolescents should be a high priority.

Current UK health policy advises that children under 16 should be encouraged to only use mobile phones for essential purposes, use a hands-free kit or send text messages and, if calls are really necessary, to keep them short.

But this is purely precautionary because there is no evidence to clearly prove whether or not phones are harmful to young people.